Heater Pump
The heater pump is required to maintain engine coolant flow to the heater core for passenger compartment heating when the engine is not running. The PCM commands the heater pump on by energizing the heater pump control relay (HPCR).
The pump is commanded on when the following conditions are met:
- The key is in the ON/START position.
- The engine coolant temperature is above a minimum threshold 0°C (32°F) nominal.
- The inferred ambient temperature is below a calibrated value 32°C (90°F) nominal.
- The engine speed is below a calibrated threshold (nominal 4,000 RPM) including engine OFF.
- The climate control mode switch is in any position other than OFF.
The pump is off when the climate control mode switch is set to OFF.